JP7199409B2 - Flame-retardant composite fiber and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flame-retardant composite fiber and a method for producing the same. In particular, the present invention relates to a flame-retardant inorganic particle-fiber composite fiber and a method for producing the same.

Techniques for improving the flame resistance of materials are being studied in various fields. For example, since wood materials such as wood and natural fibers are relatively flammable, they are treated with chemicals such as flame retardants to make them less flammable (Patent Documents 1 and 2).

On the other hand, fibers such as wood fibers exhibit various properties based on the functional groups on their surfaces. Techniques for questioning have been developed. For example, regarding the technique of depositing inorganic particles on fibers such as cellulose fibers, Patent Document 3 describes a composite in which crystalline calcium carbonate is mechanically bonded on fibers. Further, Patent Document 4 describes a technique for producing a composite of pulp and calcium carbonate by precipitating calcium carbonate in a pulp suspension by a carbon dioxide gas method.

JP-A-8-73212 Japanese Patent Application Laid-Open No. 2003-291110 JP-A-06-158585 U.S. Pat. No. 5,679,220

However, conventionally, when fibers are treated with a flame retardant or the like, the fibers tend to become hard and brittle, and the suppleness of the fibers may be impaired. In addition, it is difficult to print on fibers treated with a fireproofing agent, and for example, it is difficult to apply processing such as printing to a fiber sheet that has been made fireproof, which limits its use.

In view of such circumstances, an object of the present invention is to provide a flame-retardant material that maintains flexibility of fibers and has excellent printability.

As a result of intensive research on the above problems, the present inventors have found that the above problems can be solved by using a composite of inorganic particles and fibers (composite fiber) instead of paper as a base material, and have completed the present invention. The present invention includes, but is not limited to, the following inventions.
(1) A conjugate fiber obtained by treating a conjugate fiber of inorganic particles and fibers with a flame retardant, wherein 15% or more of the surface of the fiber is coated with the inorganic particles.
(2) The composite fiber according to (1), wherein the flame retardant is a boron-based flame retardant or a silicon-based flame retardant.
(3) The composite fiber according to (1) or (2), wherein the fibers are cellulose fibers.
(4) The composite fiber according to (1) or (2), wherein the inorganic particles are at least one inorganic particle selected from the group consisting of barium sulfate, magnesium carbonate and hydrotalcite.
(5) The composite fiber according to (1) to (4), wherein the inorganic particles have an average primary particle size of 1.5 μm or less.
(6) The conjugate fiber according to any one of (1) to (5), wherein the weight ratio of the fibers to the inorganic particles is 5/95 to 95/5.
(7) The conjugate fiber according to any one of (1) to (6), which is in the form of sheet, mold, board or block.
(8) The composite fiber according to any one of (1) to (7), wherein the flame retardant is a phosphorus agent and/or a nitrogen agent.
(9) The composite fiber according to any one of (1) to (8), wherein the inorganic particles contain calcium carbonate or silica/alumina.
(10) A method for producing a composite fiber according to any one of (1) to (9), comprising the step of treating the composite fiber of the inorganic particles and the fiber with a flame retardant.
(11) The method according to (10), wherein the flame retardant is impregnated, applied or sprayed.
(12) The method according to (10), comprising synthesizing inorganic particles in a fiber-containing liquid to obtain the composite fiber.

According to the present invention, by using a composite material in which the fiber surfaces are coated with inorganic particles, each fiber becomes difficult to burn due to the inorganic particles, and a particularly excellent flame-retardant sheet can be obtained. In addition, when the conjugate fiber of the present invention is made into a sheet, not only the fibers but also the inorganic particles are present at a high density. can be maintained. Furthermore, by using a composite fiber sheet as a base material, it is possible to obtain a composite fiber sheet with excellent print quality by suppressing blurring and deterioration of color development due to chemical treatment during inkjet printing.

FIG. 1 is a schematic diagram of the synthesizing apparatus used in the experiment. FIG. 2 is a schematic diagram of the synthesizing apparatus used in the experiment. FIG. 3 is an electron micrograph of the composite (Sample 1) used in the experiment (left: 3,000 times, right: 50,000 times). FIG. 4 is an electron micrograph of the composite (Sample 2) used in the experiment (left: 3,000 times; right: 10,000 times). FIG. 5 is an electron micrograph of the composite (Sample 3) used in the experiment (left: 3,000 times, right: 50,000 times). FIG. 6 is an electron micrograph of the composite (Sample 4) used in the experiment (left: 3,000 times; right: 50,000 times). FIG. 7 is an electron micrograph of the composite (Sample 5) used in the experiment (left: 3,000 times; right: 50,000 times). FIG. 8 is a schematic diagram of an apparatus used for synthesizing sample 6. FIG. FIG. 9 is a schematic diagram of an apparatus used for synthesizing sample 6 (ultra-fine bubble generator). FIG. 10 is an electron micrograph of the composite (Sample 6) used in the experiment (left: 3,000 times, right: 50,000 times). FIG. 11 is a photograph showing the flammability test of Experiment 3. FIG. FIG. 12 is a photograph showing the state of the combustibility test of Experiment 3. FIG. 13 is a photograph showing the results of the combustibility test of Experiment 3. FIG. FIG. 14 is a photograph showing the flammability test of Experiment 3. FIG. FIG. 15 is a photograph showing the flammability test of Experiment 3. FIG. FIG. 16 is a photograph showing the flammability test of Experiment 3. FIG.

The present invention relates to composite fibers (composites) treated with a flame retardant. In the present invention, by using a composite fiber in which inorganic particles are fixed to the fiber as a base material, a textile product having excellent printability even after being treated with a flame retardant can be obtained.

Flame Retardant In the present invention, "flame retardant" means difficult to burn; means an additive to make the material less flammable. Depending on the materials and their uses, laws and regulations have been established, and detailed standards and evaluation methods regarding "flame retardancy" have been standardized. Among them, terms such as "noncombustible" meaning that it cannot burn with flame, "flameproof" meaning that fire does not spread, and other terms such as "fireproof" and "fireproof" are used. However, in the present invention, all of these terms are defined as “flame retardant”.

A flame retardant, sometimes called a non-combustible (improving) agent, is a chemical that improves the resistance to burning of a treated material. In the present invention, the composite fiber will be treated with a flame retardant. The flame retardant to be used is not particularly limited, but examples thereof include boron-based flame retardants containing boron atoms such as boric acid or salts thereof, polyborates, and zinc borate. Silicon-based flame retardants containing silicon atoms, such as silicates and silicones, can also be suitably used. In addition, nitrogen-based flame retardants containing nitrogen atoms such as guanidine or its salts, ammonium sulfate, and melamine sulfate, phosphoric acid or its salts, polyphosphates, diethylethylphosphonate, dimethyl (methacryloyloxyethyl phosphate), Diethyl-2-(acryloyloxy)ethyl phosphate, triethyl phosphate, diethyl-2-(methacryloylethyl) phosphate, triphenyl phosphate, tricresyl phosphate, phosphate esters, phosphorus-based refractories containing phosphorus atoms such as red phosphorus Combustion agents, compounds containing phosphorus and nitrogen elements (melamine phosphate, guanidine phosphate, guanylurea phosphate, melamine metaphosphate, melamine polyphosphate, melamine-coated ammonium polyphosphate), guanidine hydrochloride, guanidine hydrobromide, etc. Brominated flame retardants such as halogen-containing amino acid salts, decabromodiphenyl ether, tetrabromobisphenol A, hexabromocyclododecane, ethylenebis(tetrabromophthalimide), bis(pentabromophenyl)ethane, hexabromobenzene, phosphorus Ammonium salts such as ammonium sulfate, ammonium sulfate, ammonium borate, ammonium sulfamate, ammonium chloride, ammonium polyphosphate, etc. Flame retardants composed of compounds containing two or more of the above elements, hydrated aluminum hydroxide, hydrated Hydrated metal compounds such as magnesium hydroxide and hydrotalcite; compounds containing antimony such as antimony trioxide, antimony tetroxide and antimony pentoxide; tin compounds such as zinc hydroxide stannate and zinc trioxide; titanium oxide Inorganic flame retardants such as metal compounds used in general pigments such as

Among the above flame retardants, agents containing boron atoms (boron-based flame retardants), agents containing silicon atoms (silicon-based flame retardants), or agents containing phosphorus atoms (phosphorus-based flame retardants) Chemical agents) and agents containing nitrogen atoms (nitrogen-based flame retardants) generate less toxic gas when burned, and are less harmful to the environment, and are therefore preferable for flame retardant treatment of various materials. Furthermore, it is known that boron-based flame retardants and silicon-based flame retardants have good compatibility with sugar compounds such as cellulose. The reason for this is that, as described in Japanese Patent Laid-Open No. 2006-233006, the hydroxyl group dehydrates at high temperatures during combustion, releasing water to exhibit a cooling effect, and forming a carbonized layer to form a heat insulating coating. It is for

As for the flame retardant, different flame retardants may be used in combination or a flame retardant aid may be used in combination, and the amount used may be adjusted according to the desired performance. The amount used is, for example, 1 to 50%, preferably 5 to 45%, more preferably 10 to 40%, based on the weight of the substrate. If the amount used is 1% or less, it is difficult to impart sufficient flame retardancy, and if it is 50% or more, the cost becomes high, which is not suitable.

These flame retardants can be treated by, for example, impregnation, coating, or spraying when they are liquids, and general impregnation and coating (coating) methods can be used. For example, forward rotation roll coater, air knife coater, blade coater, bill blade coater, two stream coater, twin blade coater, rod coater (bar coater), gate roll coater, reverse roll coater, gravure roll coater, notch bar coater, die coater , a bead coater, a curtain coater, an impregnation coater, a Seiden coater, a spray coater, or the like, can be used to apply the flame retardant.

The flame-retardant treatment may be performed before, during, or after molding into a sheet, mold, board, block, or the like. If treated before or during molding, the process can be shortened, and if treated after molding, the content of the flame retardant can be easily adjusted.

Composite Fibers Surface -Coated with Inorganic Particles The present invention uses fibers whose surfaces are coated with inorganic particles. In a particularly preferred embodiment of the present invention, a fiber-inorganic composite in which 15% or more of the fiber surface is coated with inorganic particles is used.

The composite fiber according to the present invention is not simply a mixture of fibers and inorganic particles, but the fibers and inorganic particles are bound by hydrogen bonding or the like, so the inorganic particles fall off from the fibers even by disaggregation treatment or the like. There are few things. The strength of binding between fibers and inorganic particles in the composite can be evaluated, for example, by numerical values such as ash retention (%, that is, ash in sheet/ash in composite before disaggregation×100). Specifically, the composite is dispersed in water and adjusted to a solid content concentration of 0.2%, and after disintegration for 5 minutes with a standard disintegrator specified in JIS P 8220-1: 2012, JIS P 8222: according to 2015. The ash retention when sheeted using a 150-mesh wire can be used for evaluation, and in a preferred embodiment, the ash retention is 20% by mass or more, and in a more preferred embodiment, the ash retention is 50% by mass or more. be.

(Inorganic particles)
In the present invention, the inorganic particles to be combined with the fibers are not particularly limited, but inorganic particles that are insoluble or sparingly soluble in water are preferred. In some cases, inorganic particles are synthesized in an aqueous system, and the fiber composite is sometimes used in an aqueous system, so it is preferable that the inorganic particles are insoluble or sparingly soluble in water.

The inorganic particles referred to here refer to metals or metal compounds. Metal compounds include metal cations (e.g., Na ⁺ , Ca ²⁺ , Mg ²⁺ , Al ³⁺ , Ba ²⁺ ) and anions (e.g., O ^2- , OH ^- , CO ₃ ^2- _A ^{generally inorganic} _{_ _ _ _} ^_ _{_} ^{_ _ _ _} Say something called salt. In the present invention, at least part of the inorganic particles are metal salts of calcium, magnesium or barium, or at least part of the inorganic particles are metal salts of silicic acid or aluminum, or titanium, copper, silver, iron, manganese Alternatively, metal particles containing zinc are preferable.

A method for synthesizing these inorganic particles may be a known method, and may be either a gas-liquid method or a liquid-liquid method. An example of the gas-liquid method is the carbon dioxide method. For example, magnesium carbonate can be synthesized by reacting magnesium hydroxide and carbon dioxide. Examples of the liquid-liquid method include neutralizing an acid (hydrochloric acid, sulfuric acid, etc.) and a base (sodium hydroxide, potassium hydroxide, etc.), reacting an inorganic salt with an acid or base, and reacting inorganic salts with each other. A method of reacting is mentioned. For example, barium sulfate is obtained by reacting barium hydroxide with sulfuric acid, aluminum hydroxide is obtained by reacting aluminum sulfate with sodium hydroxide, and calcium and aluminum are obtained by reacting calcium carbonate with aluminum sulfate. Composite inorganic particles can be obtained. In addition, when synthesizing inorganic particles in this way, any metal or metal compound can coexist in the reaction solution. can be For example, composite particles of calcium phosphate and titanium can be obtained by allowing titanium dioxide to coexist in the reaction solution when phosphoric acid is added to calcium carbonate to synthesize calcium phosphate.

In the case of synthesizing calcium carbonate, for example, calcium carbonate can be synthesized by a carbon dioxide method, a soluble salt reaction method, a lime/soda method, a soda method, or the like. In a preferred embodiment, calcium carbonate is synthesized by a carbon dioxide method. Synthesize.

In general, when producing calcium carbonate by the carbon dioxide method, lime is used as a calcium source, and water is added to quicklime CaO to obtain slaked lime Ca ₍ OH) ₂ . Calcium carbonate is synthesized by a carbonation process in which CaCO 3 is blown to obtain calcium carbonate CaCO ₃ . At this time, a suspension of slaked lime prepared by adding water to quicklime may be passed through a screen to remove low-soluble lime grains contained in the suspension. Alternatively, slaked lime may be directly used as a calcium source. When synthesizing calcium carbonate by the carbon dioxide gas method in the present invention, the carbonation reaction can also be carried out in the presence of cavitation bubbles.

In general, a gas-blown carbonator and a mechanically stirred carbonator are known as a reaction vessel (carbonation reactor: carbonator) for producing calcium carbonate by the carbon dioxide method. In the gas-blown carbonator, carbon dioxide gas is blown into a carbonation reaction tank containing slaked lime suspension (milk of lime), causing the reaction between the slaked lime and carbon dioxide gas. is difficult to control uniformly and finely, and there is a limit in terms of reaction efficiency. On the other hand, in a mechanically stirred carbonator, a stirrer is installed inside the carbonator, and by introducing carbon dioxide gas near the stirrer, the carbon dioxide gas is made into fine bubbles and the reaction efficiency between slaked lime and carbon dioxide gas is improved. ("Cement, Gypsum, Lime Handbook" Gihodo Publishing, 1995, p. 495).

However, when stirring with a stirrer installed inside the carbonation reaction tank, such as a mechanically stirred carbonator, if the concentration of the reaction solution is high or the carbonation reaction progresses, the resistance of the reaction solution will increase and sufficient stirring will be difficult. Therefore, it is difficult to control the carbonation reaction accurately, and a considerable load is applied to the stirrer to perform sufficient stirring, which is disadvantageous in terms of energy. Also, the gas inlet is at the bottom of the carbonator, and the stirrer blades are placed near the bottom of the carbonator for good stirring. The less soluble lime screen residue settles so quickly that it always stays at the bottom, blocking gas inlets and unbalancing agitators. Furthermore, in the conventional method, in addition to the carbonator, a stirrer and equipment for introducing carbon dioxide gas into the carbonator are required, and the equipment is costly. In the mechanically stirred carbonator, the carbon dioxide gas supplied near the stirrer is finely divided by the stirrer to improve the reaction efficiency between the slaked lime and carbon dioxide gas. can not be finely divided, and in terms of the carbonation reaction, it is sometimes difficult to accurately control the form of calcium carbonate to be produced. By synthesizing calcium carbonate in the presence of cavitation bubbles, it becomes possible to efficiently proceed the carbonation reaction and produce uniform calcium carbonate microparticles. In particular, by using jet cavitation, sufficient stirring can be performed without a mechanical stirrer such as a blade. In the present invention, a conventionally known reaction vessel can be used, and of course, a gas-blown carbonator or a mechanically stirred carbonator such as those described above can be used without any problems, and these vessels can be equipped with nozzles and the like. may be combined with jet cavitation using

When calcium carbonate is synthesized by the carbon dioxide gas method, the solid content concentration of the aqueous suspension of slaked lime is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, and still more preferably 1 to 20%. % by weight. If the solid content concentration is low, the reaction efficiency will be low and the production cost will be high. When calcium carbonate is synthesized in the presence of cavitation bubbles, the reaction solution and carbon dioxide gas can be suitably mixed even when a suspension (slurry) having a high solid content is used.

As the aqueous suspension containing slaked lime, those generally used for synthesis of calcium carbonate can be used. can be prepared. The conditions for slaking are not particularly limited, but for example, the concentration of CaO is 0.1% by weight or more, preferably 1% by weight or more, and the temperature is 20 to 100°C, preferably 30 to 100°C. . Also, the average residence time in the slaking reaction tank (slaker) is not particularly limited, but can be, for example, 5 minutes to 5 hours, preferably 2 hours or less. Of course, the slaker may be batch or continuous. In the present invention, the carbonation reaction tank (carbonator) and the slaked reaction tank (slaker) may be separated, or one reaction tank may be used as both the carbonation reaction tank and the slaked reaction tank. good.

When synthesizing magnesium carbonate, a method for synthesizing magnesium carbonate can be according to a known method. For example, magnesium bicarbonate can be synthesized from magnesium hydroxide and carbon dioxide gas, and basic magnesium carbonate can be synthesized from magnesium bicarbonate via normal magnesium carbonate. Magnesium carbonate can be obtained as magnesium bicarbonate, normal magnesium carbonate, basic magnesium carbonate, etc. by a synthesis method, but it is particularly preferable to use basic magnesium carbonate as the magnesium carbonate related to the composite fiber of the present invention. This is because magnesium bicarbonate has relatively low stability, and normal magnesium carbonate, which is a columnar (needle) crystal, may be difficult to fix to fibers. On the other hand, by chemically reacting even basic magnesium carbonate in the presence of fibers, it is possible to obtain composite fibers of magnesium carbonate and fibers coated with scales on the surface of the fibers.

Further, in the present invention, the reaction liquid in the reaction vessel can be circulated for use. By circulating the reaction liquid in this way and increasing the contact between the reaction liquid and carbon dioxide gas, the reaction efficiency is increased, and the desired inorganic particles can be easily obtained.

In the present invention, a gas such as carbon dioxide (carbon dioxide gas) is blown into the reaction vessel and can be mixed with the reaction solution. According to the present invention, carbon dioxide gas can be supplied to the reaction solution without a gas supply device such as a fan or blower, and the carbon dioxide gas is finely divided by cavitation bubbles or ultra-fine bubbles, so that the reaction can be efficiently carried out. It can be carried out.

In the present invention, the carbon dioxide concentration of the gas containing carbon dioxide is not particularly limited, but a higher carbon dioxide concentration is preferred. The amount of carbon dioxide gas to be introduced into the injector is not limited and can be selected as appropriate.

The carbon dioxide-containing gas of the present invention may be substantially pure carbon dioxide gas or may be a mixture with other gases. For example, in addition to carbon dioxide gas, gases containing inert gases such as air and nitrogen can be used as gases containing carbon dioxide. As the gas containing carbon dioxide, in addition to carbon dioxide gas (carbon dioxide gas), exhaust gases discharged from incinerators, coal boilers, heavy oil boilers, etc. in paper mills can be suitably used as carbon dioxide-containing gases. In addition, the carbonation reaction can also be performed using carbon dioxide generated from the lime calcination process.

When synthesizing barium sulfate (BaSO ₄ ), barium sulfate (BaSO ₄ ) is an ionic crystalline compound consisting of barium ions and sulfate ions, and is often plate-like or column-like. is sparingly soluble. Pure barium sulfate is a colorless crystal, but if it contains impurities such as iron, manganese, strontium, and calcium, it becomes yellowish brown or blackish gray and translucent. It can be obtained as a natural mineral, but it can also be synthesized through chemical reactions. In particular, products synthesized by chemical reactions are used for medical purposes (X-ray contrast agents), and are also widely used for paints, plastics, storage batteries, etc. by applying their chemically stable properties.

In the present invention, composite fibers of barium sulfate and fibers can be produced by synthesizing barium sulfate in solution in the presence of fibers. Examples thereof include a method of reacting an acid (such as sulfuric acid) and a base by neutralization, a method of reacting an inorganic salt with an acid or a base, and a method of reacting inorganic salts with each other. For example, barium sulfate can be obtained by reacting barium hydroxide with sulfuric acid or aluminum sulfate, or barium sulfate can be precipitated by adding barium chloride to an aqueous solution containing sulfate.

When synthesizing hydrotalcite, a known method can be used for synthesizing hydrotalcite. For example, fibers are immersed in a carbonate aqueous solution and an alkaline solution (such as sodium hydroxide) containing carbonate ions constituting an intermediate layer in a reaction vessel, and then an acid solution (divalent metal ions and trivalent metal ions constituting the basic layer). A metal salt aqueous solution containing metal ions) is added, and the temperature, pH, etc. are controlled, and a coprecipitation reaction is performed to synthesize hydrotalcite. In addition, in the reaction vessel, the fibers are immersed in an acid solution (a metal salt aqueous solution containing divalent metal ions and trivalent metal ions constituting the basic layer), and then a carbonate aqueous solution containing carbonate ions constituting the intermediate layer. and an alkaline solution (sodium hydroxide, etc.) are added dropwise, and the temperature, pH, etc. are controlled, and a coprecipitation reaction can be performed to synthesize hydrotalcite. Although the reaction is generally carried out under normal pressure, there is also a method of hydrothermal reaction using an autoclave or the like (JP-A-60-6619).

In the present invention, various chlorides, sulfides, nitrates, and sulfates of magnesium, zinc, barium, calcium, iron, copper, cobalt, nickel, and manganese are used as a source of divalent metal ions constituting the basic layer. can be used. Various chlorides, sulfides, nitrates, and sulfates of aluminum, iron, chromium, and gallium can be used as a source of trivalent metal ions constituting the basic layer.

In the present invention, carbonate ions, nitrate ions, chloride ions, sulfate ions, phosphate ions, and the like can be used as interlayer anions. Sodium carbonate is used as the source when carbonate is the interlayer anion. However, sodium carbonate can be replaced by a gas containing carbon dioxide (carbon dioxide gas), and may be substantially pure carbon dioxide gas or a mixture with other gases. For example, exhaust gases discharged from paper mill incinerators, coal boilers, heavy oil boilers, etc. can be suitably used as the carbon dioxide-containing gas. In addition, the carbonation reaction can also be performed using carbon dioxide generated from the lime calcination process.

When synthesizing alumina and/or silica, one or more inorganic acids or aluminum salts are used as reaction starting materials, and alkali silicate salts are added to synthesize them. It is possible to synthesize by using an alkali silicate as a starting material and adding one or more of an inorganic acid or an aluminum salt, but the use of an inorganic acid and/or an aluminum salt as a starting material is preferable The fixation of the material to the fibers is good. The composite fiber of silica and/or alumina obtained by the present invention has a Si/Al ratio of 4 or more as a result of measurement by fluorescent X-ray diffraction of ash baked in an electric furnace at 525° C. for 2 hours. It is preferably 4-30, more preferably 4-20, more preferably 4-10. In addition, since the silica and/or alumina obtained in the present invention are amorphous substances, no distinct peaks derived from crystallinity are detected when the same ash is measured by X-ray diffraction. The inorganic acid is not particularly limited, and for example, sulfuric acid, hydrochloric acid, nitric acid, etc. can be used. Among these, sulfuric acid is particularly preferred from the viewpoint of cost and handling. Examples of aluminum salts include aluminum sulfate, aluminum chloride, polyaluminum chloride, alum, potassium alum, etc. Among them, aluminum sulfate can be preferably used. Alkaline silicates include sodium silicate and potassium silicate, and sodium silicate is preferred because it is readily available. The molar ratio of silicic acid and alkali may be any, but silicic acid No. 3 generally distributed has a molar ratio of SiO ₂ :Na ₂ O=3 to 3.4:1, which is preferable. can be used. In the present invention, water is used for preparation of suspensions and the like, and as this water, ordinary tap water, industrial water, ground water, well water, etc. can be used, as well as ion-exchanged water, distilled water, Ultrapure water, industrial wastewater, and water obtained in the carbonation process can be suitably used.

When synthesizing calcium sulfate, a known method can be used to synthesize calcium sulfate. For example, calcium sulfate can be synthesized as a salt obtained by immersing fibers in a reaction vessel and neutralizing sulfuric acid and calcium hydroxide in the system.

When synthesizing calcium silicate, a method for synthesizing calcium silicate can be based on a known method. For example, it can be obtained by hydrothermal synthesis by adding a calcium source such as calcium oxide or calcium hydroxide and a silica source such as α-quartz to an autoclave.

The composite fibers of the present invention can be obtained by synthesizing inorganic particles in the presence of fibers such as cellulose fibers. This is because the fiber surface becomes a suitable place for the precipitation of inorganic particles, and thus the conjugate fiber can be easily synthesized. As a method for synthesizing the composite fiber, for example, a composite may be synthesized by stirring and mixing a solution containing the precursor of the fiber and the inorganic particles in an open reaction tank, or the precursor of the fiber and the inorganic particle may be synthesized. may be synthesized by injecting an aqueous suspension containing into the reaction vessel. As will be described later, cavitation bubbles or ultra-fine bubbles may be generated when an aqueous suspension of an inorganic precursor is injected into the reaction vessel, and the inorganic particles may be synthesized in the presence of such bubbles.

In the present invention, the liquid may be injected into the reaction vessel under conditions that generate cavitation bubbles or ultra-fine bubbles, or may be injected under conditions that do not generate cavitation bubbles or ultra-fine bubbles. Also, the reaction vessel is preferably a pressure vessel in any case. In addition, the pressure vessel in the present invention means a vessel to which a pressure of 0.005 MPa or more can be applied. Under conditions that do not cause cavitation bubbles, the pressure in the pressure vessel is preferably 0.005 MPa or more and 0.9 MPa or less in terms of static pressure.

(Cavitation bubbles)
When synthesizing the composite fiber according to the present invention, inorganic particles can be precipitated in the presence of cavitation bubbles. In the present invention, cavitation is a physical phenomenon in which bubbles are generated and disappear in a short time due to a pressure difference in a fluid flow, and is also called a cavitation phenomenon. Bubbles caused by cavitation (cavitation bubbles) are generated with very small "bubble nuclei" of 100 microns or less existing in the liquid as nuclei when the pressure in the fluid becomes lower than the saturated vapor pressure for a very short time.

In the present invention, cavitation bubbles can be generated in the reaction vessel by a known method. For example, generating cavitation bubbles by injecting a fluid at high pressure, generating cavitation by agitating the fluid at high speed, generating cavitation by generating an explosion in the fluid, and ultrasonic vibration. It is conceivable that cavitation is generated by the child (vibratory cavitation).

In particular, in the present invention, it is preferable to generate cavitation bubbles by injecting a fluid at high pressure because it is easy to generate and control cavitation bubbles. In this mode, by compressing the injection liquid using a pump or the like and injecting it through the nozzle at high speed, cavitation bubbles are generated at the same time as the liquid itself expands due to the extremely high shear force and sudden pressure reduction in the vicinity of the nozzle. . The method using a fluid jet has a high cavitation bubble generation efficiency, and can generate cavitation bubbles having a stronger collapse impact force. In the present invention, controlled cavitation bubbles are made to exist when synthesizing inorganic particles, and are clearly different from cavitation bubbles that naturally occur in fluid machinery and cause uncontrollable harm.

In the present invention, cavitation can be generated by directly using the reaction solution such as the raw material as the injection liquid, or cavitation bubbles can be generated by injecting some fluid into the reaction vessel. The fluid in which the liquid jet forms a jet may be liquid, gas, solid such as powder or pulp, or a mixture thereof, as long as it is in a fluid state. Furthermore, if necessary, another fluid such as carbon dioxide gas can be added to the above fluid as a new fluid. The fluid and the new fluid may be uniformly mixed and jetted, or may be jetted separately.

A liquid jet is a liquid or a jet of fluid in which solid particles or gas is dispersed or mixed in the liquid, and refers to a liquid jet containing raw material slurry of pulp or inorganic particles or air bubbles. The gas referred to here may contain bubbles due to cavitation.

Flow velocity and pressure are particularly important because cavitation occurs when a liquid is accelerated and the local pressure is lower than the liquid's vapor pressure. From this, the basic dimensionless number representing the cavitation state, the cavitation number (Cavitation Number) σ, is defined as the following formula 1 (Edited by Yoji Kato, "New Edition Cavitation: Basics and Recent Progress", Maki Shoten , 1999).

Here, a large cavitation number indicates that the flow field is in a state where cavitation is unlikely to occur. Especially when cavitation is generated through a nozzle such as a cavitation jet or an orifice pipe, the cavitation number σ is given by the following equation (2) from the nozzle upstream pressure p1, the nozzle downstream pressure p2, and the saturated vapor pressure pv of the sample water. In a cavitation jet, the pressure difference between p1, p2, and pv is large, and p1>>p2>>pv, so the cavitation number σ can be further approximated as shown in Equation 2 below. (H. Soyama, J. Soc. Mat. Sci. Japan, 47(4), 381, 1998).

As for the cavitation conditions in the present invention, the cavitation number σ described above is preferably 0.001 or more and 0.5 or less, preferably 0.003 or more and 0.2 or less, and 0.01 or more and 0.1 or less. is particularly preferred. When the cavitation number σ is less than 0.001, the pressure difference with the surroundings when the cavitation bubble collapses is low, so the effect is small. less likely to occur.

Further, when cavitation is generated by injecting the injection liquid through a nozzle or an orifice pipe, the pressure of the injection liquid (upstream pressure) is desirably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 20 MPa or less. 2 MPa or more and 15 MPa or less is more preferable. If the upstream pressure is less than 0.01 MPa, it is difficult to generate a pressure difference with the downstream pressure, and the effect is small. On the other hand, when the pressure is higher than 30 MPa, a special pump and pressure vessel are required, and the energy consumption increases, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream pressure) is preferably 0.005 MPa or more and 0.9 MPa or less in terms of static pressure. Also, the ratio of the pressure in the container to the pressure of the injection liquid is preferably in the range of 0.001 to 0.5.

In the present invention, the inorganic particles can also be synthesized by injecting the injection liquid under conditions that do not generate cavitation bubbles. Specifically, the pressure of the injection liquid (upstream pressure) is set to 2 MPa or less, preferably 1 MPa or less, and the pressure of the injection liquid (downstream pressure) is more preferably set to 0.05 MPa or less.

The jet velocity of the liquid jet is preferably in the range of 1 m/sec to 200 m/sec, more preferably in the range of 20 m/sec to 100 m/sec. If the velocity of the jet is less than 1 m/sec, the effect is weak because the pressure drop is low and cavitation is less likely to occur. On the other hand, if it is more than 200 m/sec, a high pressure is required and a special device is required, which is disadvantageous in terms of cost.

In the present invention, cavitation may be generated in a reaction vessel for synthesizing inorganic particles. In addition, it is possible to process in one pass, but it is also possible to circulate as many times as necessary. Furthermore, multiple generators can be used to process in parallel or in sequence.

The injection of liquid for generating cavitation may be done in a container open to the atmosphere, but is preferably done in a pressure vessel to control cavitation.

When cavitation is generated by liquid injection, the solid content concentration of the reaction solution is preferably 30% by weight or less, more preferably 20% by weight or less. This is because such a concentration makes it easier for the cavitation bubbles to act uniformly on the reaction system. Further, the aqueous suspension of slaked lime, which is the reaction solution, preferably has a solid content concentration of 0.1% by weight or more from the viewpoint of reaction efficiency.

In the present invention, for example, when synthesizing a composite of calcium carbonate and cellulose fibers, the pH of the reaction solution is basic at the start of the reaction, but changes to neutral as the carbonation reaction progresses. Therefore, the reaction can be controlled by monitoring the pH of the reaction solution.

In the present invention, by increasing the injection pressure of the liquid, the flow velocity of the injection liquid increases, the pressure decreases accordingly, and stronger cavitation can be generated. In addition, by increasing the pressure in the reaction vessel, the pressure in the region where the cavitation bubbles collapse increases, and the pressure difference between the bubbles and the surroundings increases, so the bubbles collapse violently and the impact force can be increased. Furthermore, dissolution and dispersion of introduced carbon dioxide gas can be promoted. The reaction temperature is preferably 0° C. or higher and 90° C. or lower, and particularly preferably 10° C. or higher and 60° C. or lower. In general, the impact force is considered to be maximum at the midpoint between the melting point and the boiling point. Therefore, a high effect can be obtained within the above range.

In the present invention, the energy required to generate cavitation can be reduced by adding a surfactant. Surfactants to be used include known or novel surfactants, for example, nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, and alkylene oxide adducts of fatty acids. , anionic surfactants, cationic surfactants, and amphoteric surfactants. It may consist of a single component or a mixture of two or more components. The amount to be added may be any amount necessary to reduce the surface tension of the jetting liquid and/or the liquid to be jetted.

As one preferred embodiment, the average primary particle size of the inorganic particles in the composite fiber of the present invention can be, for example, 1.5 μm or less. , 300 nm or less, and an average primary particle size of 200 nm or less, 150 nm or less, or 100 nm. Also, the average primary particle size of the inorganic particles can be 10 nm or more, 30 nm or more, or 50 nm or more. The average primary particle size can be measured using an electron micrograph.

In addition, the inorganic particles in the composite fiber of the present invention may take the form of secondary particles in which fine primary particles are aggregated, and the secondary particles can be generated according to the application by the aging process, and by pulverization. Agglomerates can also be broken down. Grinding methods include ball mills, sand grinder mills, impact mills, high pressure homogenizers, low pressure homogenizers, dyno mills, ultrasonic mills, Kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, disaggregators, and beaters. , short-screw extruders, twin-screw extruders, ultrasonic stirrers, household juicer mixers, and the like.

(fiber)
The composite fiber used in the present invention is a composite of cellulose fiber and inorganic particles. As the cellulose fibers constituting the composite fibers, for example, natural cellulose fibers, as well as regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, and synthetic fibers can be used without limitation. Examples of raw materials for cellulose fibers include plant-derived pulp fibers, cellulose nanofibers, bacterial cellulose, animal-derived cellulose such as sea squirts, and algae. Wood pulp may be produced by pulping wood raw materials. Wood raw materials include red pine, black pine, Sakhalin fir, spruce, red pine, larch, fir, hemlock, cedar, cypress, larch, white fir, spruce, hiba, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, Coniferous trees such as Mercury pine and radiata pine, and mixtures of these, broadleaf trees such as beech, birch, alder, oak, tab, chinensis, white birch, cotton willow, poplar, ash, willow, eucalyptus, mangrove, lauan, and acacia, and mixtures thereof material is exemplified.

The method of pulping natural materials such as wood raw materials (woody raw materials) is not particularly limited, and examples thereof include pulping methods commonly used in the paper industry. Wood pulp can be classified by pulping method, for example, chemical pulp cooked by methods such as Kraft method, sulfite method, soda method, polysulfide method; mechanical pulp obtained by mechanical power such as refiner and grinder; semi-chemical pulp obtained by mechanical pulping after pretreatment with a cellulose; waste paper pulp; deinked pulp, and the like. The wood pulp may be unbleached (before bleaching) or bleached (after bleaching).

Examples of non-wood-derived pulp include cotton, hemp, sisal hemp, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, kozo, mitsumata, and the like.

The pulp fibers may be either unbeaten or beaten, and may be selected depending on the application of the composite fiber. By beating, it is possible to improve the strength of the sheet, improve the BET specific surface area, and promote the fixation of the inorganic particles. On the other hand, by using the conjugate fiber in an unbeaten state, it is possible to suppress the risk of detachment of the inorganic matter together with the fibril when the composite fiber is stirred or kneaded in the matrix, and it can also be used as a reinforcing material for cement and the like. In some cases, the fiber length can be kept long, so the effect of improving the strength becomes high. The degree of fiber beating can be represented by the Canadian Standard freeness (CSF) specified in JIS P 8121-2:2012. As the beating progresses, the drainage state of the fibers decreases and the freeness decreases. Fibers of any freeness can be used for synthesizing the conjugate fiber, but fibers of 600 mL or less can also be suitably used. For example, when a sheet is produced using the conjugate fiber of the present invention, it is possible to suppress paper breakage during continuous papermaking of cellulose fibers having a freeness of 600 mL or less. In other words, if treatment to increase the fiber surface area, such as beating, is performed to improve the strength and specific surface area of the composite fiber sheet, the freeness will be lowered, but cellulose fibers that have been subjected to such treatment can also be suitably used. Moreover, the lower limit of the freeness of the cellulose fibers is more preferably 50 mL or more, and still more preferably 100 mL or more. If the freeness of the cellulose fibers is 200 mL or more, the operability of continuous papermaking is good.

In addition, these cellulose raw materials are further processed to obtain powdered cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofibers: CNF (microfibrillated cellulose: MFC, TEMPO-oxidized CNF, phosphorylated CNF, carboxymethylated CNF, mechanical pulverized CNF, etc.) can also be used. As the powdered cellulose used in the present invention, for example, an undegraded residue obtained after acid hydrolysis of selected pulp is purified, dried, pulverized, and sieved. A crystalline cellulose powder having a distribution may be used, or commercially available products such as KC Floc (manufactured by Nippon Paper Industries), Ceorus (manufactured by Asahi Kasei Chemicals), and Avicel (manufactured by FMC) may be used. The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 1500, the crystallinity of powdered cellulose by X-ray diffraction method is preferably 70 to 90%, and the volume average particle diameter by laser diffraction particle size distribution analyzer. is preferably 1 μm or more and 100 μm or less. The oxidized cellulose used in the present invention can be obtained, for example, by oxidation in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, or mixtures thereof. can. As cellulose nanofibers, a method of defibrating the above cellulose raw material is used. As a defibration method, for example, an aqueous suspension of chemically modified cellulose such as cellulose or oxidized cellulose is mechanically ground or beaten by a refiner, a high-pressure homogenizer, a grinder, a uniaxial or multiaxial kneader, a bead mill, or the like. A method of defibrating can be used. Cellulose nanofibers may be produced by combining one or more of the above methods. The fiber diameter of the produced cellulose nanofibers can be confirmed by electron microscope observation or the like, and is, for example, in the range of 5 nm to 1000 nm, preferably 5 nm to 500 nm, more preferably 5 nm to 300 nm. When producing the cellulose nanofibers, before and/or after defibrating and/or refining the cellulose, an optional compound may be further added to react with the cellulose nanofibers to modify the hydroxyl groups. can. Functional groups to be modified include acetyl group, ester group, ether group, ketone group, formyl group, benzoyl group, acetal, hemiacetal, oxime, isonitrile, allene, thiol group, urea group, cyano group, nitro group and azo group. , aryl group, aralkyl group, amino group, amide group, imide group, acryloyl group, methacryloyl group, propionyl group, propioloyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group , decanoyl group, undecanoyl group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, acyl group such as cinnamoyl group, 2-methacryloyloxyethyl isocyanate isocyanate group such as noyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, alkyl group such as stearyl group, oxirane group, oxetane group, oxyl group, thiirane group, thietane group and the like. Hydrogen in these substituents may be substituted with a functional group such as a hydroxyl group or a carboxyl group. Moreover, a part of the alkyl group may be an unsaturated bond. The compounds used to introduce these functional groups are not particularly limited, and examples thereof include compounds having a group derived from phosphoric acid, compounds having a group derived from carboxylic acid, compounds having a group derived from sulfuric acid, and compounds derived from sulfonic acid. group, a compound having an alkyl group, a compound having an amine-derived group, and the like. The compound having a phosphate group is not particularly limited, but examples thereof include phosphoric acid and lithium salts of phosphoric acid such as lithium dihydrogen phosphate, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, and lithium polyphosphate. . Furthermore, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate and sodium polyphosphate, which are sodium salts of phosphoric acid, may be mentioned. Furthermore, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate, which are potassium salts of phosphoric acid, may be mentioned. Furthermore, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium polyphosphate, etc., which are ammonium salts of phosphoric acid, can be used. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, and ammonium salt of phosphoric acid are preferable from the viewpoint of high efficiency of introduction of phosphoric acid group and easy industrial application, and sodium dihydrogen phosphate. , Disodium hydrogen phosphate is more preferable, but not particularly limited. The compound having a carboxyl group is not particularly limited, but includes dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. . Acid anhydrides of compounds having a carboxyl group are not particularly limited, but include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. be done. Derivatives of compounds having a carboxyl group are not particularly limited, but include imidized acid anhydrides of compounds having a carboxyl group and derivatives of acid anhydrides of compounds having a carboxyl group. Examples of imidized acid anhydrides of compounds having a carboxyl group include, but are not particularly limited to, imidized dicarboxylic acid compounds such as maleimide, succinimide and phthalimide. The acid anhydride derivative of a compound having a carboxyl group is not particularly limited. For example, at least part of the hydrogen atoms of the acid anhydride of the compound having a carboxyl group, such as dimethylmaleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride, is a substituent (e.g., an alkyl group, a phenyl group, etc.). ) is substituted with. Among the compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferable because they are industrially applicable and easily gasified, but are not particularly limited. In addition, the cellulose nanofibers may be modified in such a manner that the modifying compound physically adsorbs to the cellulose nanofibers without chemically bonding them. Examples of the physically adsorbable compound include surfactants, which may be anionic, cationic or nonionic. When the above modification is performed before defibrating and/or pulverizing the cellulose, these functional groups can be eliminated after defibrating and/or pulverizing to restore the original hydroxyl groups. By applying the above modifications, it is possible to accelerate the defibration of the cellulose nanofibers and facilitate mixing with various substances when using the cellulose nanofibers.

The fibers shown above may be used singly or in combination. For example, fibrous material recovered from paper mill effluents may be fed to the carbonation reaction of the present invention. By supplying such a substance to a reaction tank, various composite particles can be synthesized, and also fibrous particles can be synthesized in terms of shape.

In the present invention, in addition to fibers, substances that can be incorporated into inorganic particles as a product to form composite particles can be used. In the present invention, fibers such as pulp fibers are used, but by synthesizing inorganic particles in a solution containing inorganic particles, organic particles, polymers, etc., these substances are further incorporated. It is possible to produce composite particles with

The fiber length of the composite fibers is not particularly limited, but for example, the average fiber length can be about 0.1 μm to 15 mm, and may be 1 μm to 12 mm, 100 μm to 10 mm, 500 μm to 8 mm, and the like.

The fiber diameter of the fibers to be combined is not particularly limited. and so on.

The fibers to be composited are preferably used in such an amount that 15% or more of the fiber surface is covered with inorganic particles. For example, the weight ratio of the fibers to the inorganic particles is 5/95 to 95/5. 10/90 to 90/10, 20/80 to 80/20, 30/70 to 70/30, 40/60 to 60/40.

In a preferred embodiment, the conjugate fiber according to the present invention has inorganic particles covering 15% or more of the fiber surface, and when the cellulose fiber surface is covered with such an area ratio, the characteristics attributed to the inorganic particles are large. while the features attributed to the fiber surface become smaller.

The conjugate fiber according to the present invention can be used in various forms, such as powder, pellets, molds, aqueous suspensions, pastes, sheets, boards, blocks, threads, and other forms. . In addition, the conjugate fiber as a main component can also be formed into a molded article such as a mold, particles, or pellets together with other materials. There are no particular restrictions on the dryer used for drying to powder, but for example, a flash dryer, band dryer, spray dryer, or the like can be preferably used.

Composite fibers according to the present invention can be used in a variety of applications, such as paper, fibers, cellulosic composite materials, filter materials, paints, plastics and other resins, rubbers, elastomers, ceramics, glass, tires, and construction. Materials (asphalt, asbestos, cement, board, concrete, brick, tile, plywood, fiberboard, veneer, ceiling material, wall material, flooring material, roofing material, etc.), furniture, various carriers (catalyst carrier, pharmaceutical carrier, agricultural chemical carrier) carriers, microorganism carriers, etc.), adsorbents (impurity removal, deodorant, dehumidification, etc.), wrinkle prevention agents, clay, abrasives, modifiers, repairing materials, heat insulating materials, heat-resistant materials, heat radiating materials, moisture-proof materials, water repellent materials, waterproof materials, light shielding materials, sealants, shielding materials, insect repellents, adhesives, medical materials, paste materials, anti-tarnishing agents, radio wave absorbers, insulation materials, sound insulation materials, interior materials, anti-vibration materials, semiconductor sealing materials , radiation shielding materials, flame retardant materials, etc. In addition, it can be used as various fillers, coating agents, etc. in the above applications. Among these, radiation shielding materials, flame retardant materials, building materials, furniture, interior materials, and heat insulating materials are preferred.

The conjugate fiber of the present invention may be applied to papermaking applications such as printing paper, newsprint, inkjet paper, PPC paper, kraft paper, fine paper, coated paper, lightly coated paper, wrapping paper, thin paper, color fine paper, Paper, cast-coated paper, non-carbon paper, label paper, thermal paper, various fancy papers, water-soluble paper, release paper, casting paper, base paper for wallpaper, flame-retardant paper (non-combustible paper), base paper for laminates, printed electronic paper, Battery separator, cushion paper, tracing paper, impregnated paper, ODP paper, construction paper (wallpaper, etc.), decorative paper, envelope paper, tape paper, heat exchange paper, synthetic fiber paper, sterilized paper, waterproof paper, greaseproof paper , heat-resistant paper, photocatalyst paper, cosmetic paper (oil-absorbing paper, etc.), various sanitary papers (toilet paper, tissue paper, wipers, diapers, sanitary products, etc.), tobacco paper, paperboard (liner, corrugating paper, white paperboard, etc.), Paper plate base paper, cup base paper, baking paper, abrasive paper, synthetic paper, and the like. That is, according to the present invention, a composite of inorganic particles and fibers having a small primary particle size and a narrow particle size distribution can be obtained. characteristics can be exhibited. Furthermore, unlike the case where the inorganic particles are simply blended with the fibers, the composite of the inorganic particles and the fibers not only facilitates the retention of the inorganic particles in the sheet, but also produces a sheet in which the inorganic particles are uniformly dispersed without agglomeration. Obtainable. Electron microscopic observation has revealed that the inorganic particles in the present invention are not only fixed on the outer surface of the fiber and inside the lumen, but also formed inside the microfibrils in a preferred embodiment.

When using the conjugate fiber of the present invention, particles generally called inorganic fillers and organic fillers and various fibers can be used together. For example, inorganic fillers include calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, delaminated kaolin). ), talc, zinc oxide, zinc stearate, titanium dioxide, silica prepared from sodium silicate and mineral acids (white carbon, silica/calcium carbonate complex, silica/titanium dioxide complex), clay, bentonite, diatomaceous earth, Calcium sulfate, zeolite, refractory clay, inorganic fillers that regenerate and utilize ash obtained in the deinking process, and inorganic fillers that form a composite with silica or calcium carbonate in the regenerating process. As the calcium carbonate-silica composite, amorphous silica such as white carbon may be used in combination with calcium carbonate and/or light calcium carbonate-silica composite. Organic fillers include urea-formalin resin, polystyrene resin, phenolic resin, hollow microparticles, acrylamide composites, wood-derived substances (fine fibers, microfibril fibers, powdered kenaf), modified insolubilized starch, ungelatinized starch, etc. is mentioned. As for fibers, there are no restrictions on natural fibers such as cellulose, synthetic fibers artificially synthesized from raw materials such as petroleum, regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, and inorganic fibers. can be used. In addition to the above, examples of natural fibers include protein-based fibers such as wool, silk threads and collagen fibers, and complex sugar chain-based fibers such as chitin/chitosan fibers and alginic acid fibers. Examples of cellulosic raw materials include plant-derived pulp fibers, bacterial cellulose, animal-derived cellulose such as sea squirt, and algae. Wood pulp may be produced by pulping wood raw materials. Wood raw materials include red pine, black pine, Sakhalin fir, spruce, red pine, larch, fir, hemlock, cedar, cypress, larch, white fir, spruce, hiba, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, Coniferous trees such as Mercury pine and radiata pine, and mixtures of these, broadleaf trees such as beech, birch, alder, oak, tab, chinensis, white birch, cotton willow, poplar, ash, willow, eucalyptus, mangrove, lauan, and acacia, and mixtures thereof material is exemplified. The method of pulping the wood raw material is not particularly limited, and an example is a pulping method commonly used in the paper industry. Wood pulp can be classified by pulping method, for example, chemical pulp cooked by methods such as Kraft method, sulfite method, soda method, polysulfide method; mechanical pulp obtained by mechanical power such as refiner and grinder; semi-chemical pulp obtained by mechanical pulping after pretreatment with a cellulose; waste paper pulp; deinked pulp, and the like. The wood pulp may be unbleached (before bleaching) or bleached (after bleaching). Examples of non-wood-derived pulp include cotton, hemp, sisal hemp, Manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, kozo, mitsumata, and the like. The wood pulp and non-wood pulp may be either unbeaten or beaten. In addition, these cellulose raw materials are further processed to obtain powdered cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofibers: CNF (microfibrillated cellulose: MFC, TEMPO-oxidized CNF, phosphorylated CNF, carboxymethylated It can also be used as CNF, mechanically ground CNF). Synthetic fibers include polyester, polyamide, polyolefin, acrylic fiber, semi-synthetic fibers include rayon, acetate, etc. Inorganic fibers include glass fiber, ceramic fiber, biosoluble ceramic fiber, carbon fiber, various metal fibers, etc. is mentioned. Regarding the above, these may be used alone or in combination of two or more.

The average particle size, shape, etc. of the inorganic particles constituting the composite fiber of the present invention can be confirmed by observation with an electron microscope. Furthermore, inorganic particles having various sizes and shapes can be composited with fibers by adjusting the conditions for synthesizing the inorganic particles.

(Synthesis of composite fiber)
In one aspect of the present invention, the composite can be synthesized by synthesizing inorganic particles in a solution containing fibers, and the method for synthesizing the inorganic particles can be according to each known method.

When barium sulfate is used as inorganic particles, barium sulfate may be synthesized in a solution containing fibers. For example, when an alkaline barium sulfate precursor typified by barium hydroxide is used as a raw material, the fibers can be swollen by dispersing the fibers in advance in a solution of the barium sulfate precursor. and fiber composites can be obtained. The reaction can be started after the swelling of the fiber is accelerated by stirring for 15 minutes or more after mixing, but the reaction may be started immediately after mixing. There are no particular restrictions on the form of the reaction vessel or stirring conditions for obtaining the present composite fiber. For example, a solution containing the fiber and barium sulfate precursor is stirred and mixed in an open reaction vessel to synthesize the composite. Alternatively, it may be synthesized by injecting an aqueous suspension containing the fiber and barium sulfate precursor into a reaction vessel. In this step, an aging time may be provided during or after the reaction for the purpose of controlling the particle size of the inorganic material and optimizing the reaction conditions (nucleation reaction and growth reaction). For example, if the inorganic substance is easily synthesized in a low pH range, that state may be maintained, or if the growth reaction of the inorganic particles takes a long time, the solution may be continuously stirred. In this case, there are no particular restrictions on the aging time or pH, and any of a neutral range of pH 6 to 8, an acidic range of pH 6 or less, and an alkaline range of pH 8 or more can be applied.

In the present invention, water is used for preparation of the suspension, etc. As this water, ordinary tap water, industrial water, ground water, well water, etc. can be used, as well as ion-exchanged water, distilled water, ultra Pure water, industrial wastewater, and water obtained when separating and dehydrating the reaction solution can be preferably used.

Further, in the present invention, the reaction liquid in the reaction vessel can be circulated for use. By circulating the reaction solution in this manner and promoting stirring of the solution, the reaction efficiency is increased, and a desired composite of inorganic particles and fibers can be easily obtained.

When producing the conjugate fiber of the present invention, various known auxiliary agents can be added. For example, chelating agents can be added, specifically polyhydroxycarboxylic acids such as citric acid, malic acid and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, iminodiacetic acid, ethylenediamine tetra Aminopolycarboxylic acids such as acetic acid and alkali metal salts thereof, alkali metal salts of polyphosphoric acids such as hexametaphosphoric acid and tripolyphosphoric acid, amino acids such as glutamic acid and aspartic acid and alkali metal salts thereof, acetylacetone, methyl acetoacetate, acetoacetic acid Examples include ketones such as allyl, sugars such as sucrose, and polyols such as sorbitol. In addition, as surface treatment agents, saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, resin acids such as alicyclic carboxylic acids and abietic acid, their salts, esters and ethers, and alcohol-based Active agents, sorbitan fatty acid esters, amide-based and amine-based surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonylphenyl ether, sodium alpha olefin sulfonate, long-chain alkylamino acids, amine oxides, alkylamines, quaternary Secondary ammonium salts, aminocarboxylic acids, phosphonic acids, polyvalent carboxylic acids, condensed phosphoric acids and the like can be added. Moreover, a dispersing agent can also be used as needed. Examples of the dispersant include sodium polyacrylate, sucrose fatty acid ester, glycerin fatty acid ester, acrylic acid-maleic acid copolymer ammonium salt, methacrylic acid-naphthoxypolyethylene glycol acrylate copolymer, methacrylic acid-polyethylene glycol. Monomethacrylate copolymer ammonium salt, polyethylene glycol monoacrylate, and the like. These can be used singly or in combination. Moreover, the timing of addition may be before or after the synthesis reaction. Such additives can be added in an amount of preferably 0.001 to 20%, more preferably 0.1 to 10%, relative to the inorganic particles.

When synthesizing the composite fiber in the present invention, the reaction conditions are not particularly limited and can be appropriately set according to the application. For example, the temperature of the synthesis reaction can be 0-90°C, preferably 10-70°C. The reaction temperature can be controlled by a temperature control device. If the temperature is too low, the reaction efficiency will decrease and the cost will increase.

Moreover, in the present invention, the reaction can be a batch reaction or a continuous reaction. Generally, batch reaction processes are preferred for the convenience of venting post-reaction residue. The scale of the reaction is not particularly limited, but the reaction may be performed on a scale of 100 L or less, or on a scale of more than 100 L. The size of the reaction vessel can be, for example, about 10 L to 100 L, 100 L to 1000 L, or about 1 m ³ (1000 L) to 100 m ³ .

Further, the reaction can be controlled by the conductivity of the reaction liquid and the reaction time. Specifically, the reaction can be controlled by adjusting the residence time of the reactant in the reaction vessel. In addition, in the present invention, the reaction can also be controlled by stirring the reaction solution in the reaction tank or making the reaction a multi-stage reaction.

In the present invention, the conjugate fiber, which is the reaction product, is obtained as a suspension, so it may be stored in a storage tank or subjected to treatments such as concentration, dehydration, pulverization, classification, aging, and dispersion as necessary. can be done. These can be carried out according to known processes, and may be appropriately determined in consideration of usage, energy efficiency, and the like. For example, the concentration/dehydration treatment is performed using a centrifugal dehydrator, a sedimentation concentration machine, or the like. Examples of this centrifugal dehydrator include decanters and screw decanters. When using a filter or dehydrator, there is no particular limitation on the type thereof, and common ones can be used. A vacuum drum dehydrator such as an Oliver filter can be suitably used to form a cake. Grinding methods include ball mills, sand grinder mills, impact mills, high pressure homogenizers, low pressure homogenizers, dyno mills, ultrasonic mills, Kanda grinders, attritors, stone mills, vibration mills, cutter mills, jet mills, disaggregators, and beaters. , short-screw extruders, twin-screw extruders, ultrasonic stirrers, household juicer mixers, and the like. Classification methods include sieves such as meshes, outward-type or inward-type slit or round-hole screens, vibrating screens, heavy-duty foreign matter cleaners, light-weight foreign matter cleaners, reverse cleaners, sieving testers, and the like. Dispersion methods include a high-speed disperser and a low-speed kneader.

The conjugate fiber in the present invention can be blended with a filler or pigment in a suspension state without being completely dehydrated, but can also be dried and powdered. The dryer in this case is also not particularly limited, but for example, a flash dryer, a band dryer, a spray dryer, or the like can be preferably used.

The conjugate fiber of the present invention can be modified by known methods. For example, in some embodiments, the surface can be made hydrophobic to enhance miscibility with resins and the like.

(Form of composite fiber)
In the present invention, by treating the above-mentioned conjugate fiber with a flame retardant, it is possible to obtain a flame-retardant conjugate fiber with greatly improved resistance to burning. The form of the obtained conjugate fiber is not particularly limited, and various moldings (body) can be produced. For example, a high-ash sheet can be easily obtained by sheeting the composite fiber of the present invention. Also, the obtained sheets can be laminated to form a multilayer sheet. Examples of paper machines used for sheet production include fourdrinier paper machines, cylinder paper machines, gap formers, hybrid formers, multi-layer paper machines, and known paper machines obtained by combining these machines. be done. Both the press linear pressure in the paper machine and the calender linear pressure in the subsequent calendering process can be determined within a range that does not interfere with the workability and the performance of the composite fiber sheet. Starch, various polymers, pigments, and mixtures thereof may be applied to the formed sheet by impregnation or coating.

A wet and/or dry paper strength agent (paper strength enhancer) may be added during sheeting. Thereby, the strength of the composite fiber sheet can be improved. Examples of paper strength agents include urea formaldehyde resin, melamine formaldehyde resin, polyamide, polyamine, epichlorohydrin resin, vegetable gum, latex, polyethyleneimine, glyoxal, gum, mannogalactan polyethyleneimine, polyacrylamide resin, polyvinylamine. , polyvinyl alcohol; composite polymers or copolymers composed of two or more of the above resins; starch and modified starch; carboxymethyl cellulose, guar gum, urea resin, and the like. The amount of the paper strength agent to be added is not particularly limited.

In addition, a high molecular weight polymer or an inorganic substance can be added in order to promote fixation of the filler to the fibers or to improve the retention of the filler or the fibers. For example, as coagulants, polyethyleneimines and modified polyethyleneimines containing tertiary and/or quaternary ammonium groups, polyalkyleneimines, dicyandiamide polymers, polyamines, polyamine/epichlorohydrin polymers, and dialkyldiallyl quaternary ammonium monomers, dialkyl Cations of aminoalkyl acrylates, dialkylaminoalkyl methacrylates, dialkylaminoalkylacrylamides, polymers of dialkylaminoalkylmethacrylamides and acrylamides, polymers of monoamines and epihalohydrin, polyvinylamines, polymers with vinylamine moieties, and mixtures thereof cation-rich amphoteric polymers obtained by copolymerizing anionic groups such as carboxyl groups and sulfone groups in the polymer molecules, and mixtures of cationic polymers and anionic or amphoteric polymers. be able to. Cationic, anionic, and amphoteric polyacrylamide-based substances can also be used as retention agents. Also, in addition to these, at least one kind of cationic or anionic polymer can be used together, so-called dual polymer retention system can be applied, and at least one kind of anionic bentonite, colloidal silica, polysilicic acid, It is a multi-component yield system that uses at least one type of inorganic fine particles such as polysilicic acid or polysilicate microgels and aluminum-modified products thereof, and organic fine particles having a particle size of 100 μm or less, which are so-called micropolymers obtained by cross-linking polymerization of acrylamide. good too. In particular, when the polyacrylamide-based substances used alone or in combination have a weight-average molecular weight of 2 million daltons or more as determined by the intrinsic viscosity method, a good yield can be obtained, preferably 5 million daltons or more, more preferably 5 million daltons or more. When is the above acrylamide-based substance of 10 million daltons or more and less than 30 million daltons, a very high yield can be obtained. The form of this polyacrylamide-based substance may be an emulsion type or a solution type. The specific composition is not particularly limited as long as the substance contains an acrylamide monomer unit as a structural unit. and quaternary ammonium salts obtained by copolymerizing acrylic acid esters. The cationic charge density of the cationic polyacrylamide-based material is not particularly limited.

In addition, depending on the purpose, drainage improver, internal sizing agent, pH adjuster, defoaming agent, pitch control agent, slime control agent, bulking agent, calcium carbonate, kaolin, talc, inorganic particles such as silica (so-called filler) and the like. The amount of each additive used is not particularly limited.

The basis weight of the sheet can be appropriately adjusted depending on the purpose, but when it is used as a building material, for example, 60 to 1200 g/m ² is preferable because the strength is high and the drying load during production is low. In order to improve flame retardancy, the higher the basic weight of the sheet (basis weight: weight per ^square meter), the more advantageous. It can also be from 2000 to 110000 g/m ² .

It is also possible to use molding methods other than sheeting, for example, a method called pulp molding, where the raw material is poured into a mold and suction dehydrated and dried, or it is spread on the surface of a molded product such as resin or metal and dried. After that, molded articles having various shapes can be obtained by a method such as peeling from the substrate. It can also be molded like plastic by mixing resin. It can also be formed into a board shape or a block shape by pressure and heat press molding, which is generally used to produce inorganic boards such as cement and gypsum. In general, the sheet can be folded and rolled up, but it can be made into a board if more strength is required. Moreover, it is also possible to mold into a block shape, which is a mass with a thickness, such as a rectangular parallelepiped or a cube. Any of the pulp molds, boards, and blocks described above can express an uneven pattern by applying a pattern to the mold at the time of molding, and can also be deformed by bending after molding.

In the compounding, drying, and molding described above, only one kind of composite can be used, or two or more kinds of composites can be mixed and used. When two or more kinds of composites are used, they can be mixed in advance, or they can be blended, dried and molded, and then mixed.

Moreover, various organic substances such as polymers and various inorganic substances such as pigments may be added to the molded composite afterward.

Moldings produced from the product of the present invention can be printed. Although this printing method is not particularly limited, for example, offset printing, silk screen printing, screen printing, gravure printing, microgravure printing, flexographic printing, letterpress printing, sticker printing, form printing, on-demand printing, fan It can be carried out by known methods such as shear roll printing and inkjet printing. Among these, inkjet printing is preferable because it does not require the preparation of a block copy unlike offset printing, and it is relatively easy to increase the size of the inkjet printer, and printing on a large sheet is also possible. In addition, since flexographic printing can be suitably printed on a molded article having relatively large unevenness on the surface, it can be suitably used when molded into a shape such as a board, a mold, or a block.

In addition, the type of pattern of the printed image formed by printing is not particularly limited. It is optional and may be a single solid color if desired.

The present invention will be described in more detail with reference to specific experimental examples, but the present invention is not limited to the following specific examples. In addition, unless otherwise specified in this specification, concentrations, parts, etc. are based on weight, and numerical ranges are described as including their end points.

In this specification, "bleached hardwood kraft pulp" is sometimes abbreviated as "LBKP" and "bleached softwood kraft pulp" is abbreviated as "NBKP" (both LBKP and NBKP are manufactured by Nippon Paper Industries). use). Also, the Canadian standard freeness (CSF) of the pulp was adjusted using a single disc refiner (SDR) or a Niagara beater. Furthermore, the average fiber length of the pulp in the pulp slurry was measured with a fiber tester (Lorentzen & Wettre).

Experiment 1. Synthesis of composite fiber of inorganic particles and fiber (Sample 1) Composite fiber of barium sulfate and aluminum hydroxide and cellulose fiber Reaction vessel (machine chest, volume: 4 m ³ ) 2% pulp slurry (bleached hardwood kraft pulp / Softwood bleached kraft pulp = 8/2, CSF = 390 mL, average fiber length: about 1.3 mm, solid content 25 kg) and barium hydroxide octahydrate (Nippon Kagaku Kogyo Co., Ltd., 75 kg) are added and mixed, and then peri Aluminum sulfate (aluminum sulfate, 98 kg) was added dropwise at about 500 g/min using a star pump. After the dropwise addition, stirring was continued for 30 minutes to obtain Sample 1 (Fig. 3).

(Sample 2) Composite fiber of magnesium carbonate and cellulose fiber 170 L of aqueous suspension containing 5250 g of magnesium hydroxide (Ube Material, UD653) and 3500 g of kraft pulp (LBKP, CSF = 360 mL, average fiber length = 0.76 mm) prepared. This was placed in a 500-L cavitation apparatus, and carbon dioxide gas was blown into the reaction vessel while circulating the reaction solution to synthesize composite fibers of fine magnesium carbonate particles and fibers by the carbon dioxide method. The reaction temperature was about 40° C., the carbon dioxide gas was supplied from a commercially available liquefied gas, and the amount of the carbon dioxide gas blown was 20 L/min. When the pH of the reaction solution reached about 7.8, the introduction of CO ₂ was stopped (the pH before the reaction was about 9.5), and then for 30 minutes, the generation of cavitation and the circulation of the slurry in the apparatus were continued. to obtain sample 2 (Fig. 4).

In synthesizing the composite fiber, cavitation bubbles were generated in the reaction vessel by circulating the reaction solution and injecting it into the reaction vessel as shown in FIG. Specifically, the reaction solution was injected at high pressure through a nozzle (nozzle diameter: 1.5 mm) to generate cavitation bubbles, but the jet velocity was about 70 m / s, and the inlet pressure (upstream pressure) was 1.8 MPa, outlet pressure (downstream pressure) was 0.3 MPa.

(Sample 3) Composite Fiber of Hydrotalcite Particles and Cellulose Fiber First, a solution for synthesizing hydrotalcite (HT) was prepared. A mixed aqueous solution of Na ₂ CO ₃ (Wako Pure Chemical Industries) and NaOH (Wako Pure Chemical Industries) was prepared as an alkaline solution (Solution A). A mixed aqueous solution of MgSO ₄ (Wako Pure Chemical Industries) and Al ₂ (SO ₄ ) ₃ (Wako Pure Chemical Industries) was prepared as an acid solution (solution B).
・Alkaline solution (solution A): _Na2CO3 concentration: 0.1M _, NaOH concentration: 1.6M
・ Acid solution (B solution): MgSO4 concentration: _{0.6M, Al2(SO4)3 concentration : 0.1M}

Next, pulp fibers (LBKP/NBKP=8/2) were added to the alkaline solution (solution A) to prepare an aqueous suspension containing pulp fibers (solid pulp content: 30 g, pulp fiber concentration: 1.56%, pH: about 12.4). This aqueous suspension was placed in a 10 L reaction vessel, and an acid solution (solution B) was added dropwise while stirring the aqueous suspension to synthesize composite fibers of hydrotalcite particles and fibers (solution A). Volume: 1.1 L, volume of B liquid: 1.1 L). Using an apparatus as shown in FIG. 2, the reaction temperature was 60° C., the dropping rate was 5 ml/min, and the dropping was stopped when the pH of the reaction solution reached about 7. After completion of dropping, the reaction solution was stirred for 30 minutes and washed with 10 times the amount of water to remove salts (Fig. 5).

(Sample 4) Composite Fibers of Hydrotalcite Particles and Cellulose Fibers Sample 4 was obtained by synthesizing in the same manner as sample 3, except that the amount of each of liquid A and liquid B was 1.6 L (FIG. 6).

(Sample 5) Composite Fiber of Silica/Alumina Particles and Cellulose Fiber 2.2 L of an aqueous suspension containing 30 g of NBKP (CSF: 510 mL) was placed in a resin container (5 L volume) and stirred with a lab mixer (500 rpm). An aqueous aluminum sulfate solution (industrial aluminum sulfate, concentration 9%) was added dropwise to this aqueous suspension for about 10 minutes until the pH reached 3.7. A sodium phosphate aqueous solution (manufactured by Wako Pure Chemical Industries, concentration 8%) was simultaneously added dropwise for about 90 minutes so as to maintain pH=4. A peristaltic pump was used for dropping, and the reaction temperature was about 24°C. After the dropwise addition, the mixture was stirred as it was for about 30 minutes, and then an aqueous sodium silicate solution (Wako Pure Chemical Industries, concentration 8%) was added dropwise for about 30 minutes to adjust the pH to 8.0. The total amounts of aluminum sulfate aqueous solution and sodium silicate aqueous solution used were 155 g and 150 g, respectively. Composite fibers of silica/alumina particles and cellulose fibers were synthesized as described above (FIG. 7).

(Sample 6) Composite Fiber of Calcium Carbonate Particles and Cellulose Fiber An aqueous suspension containing pulp fibers (LBKP/NBKP=8/2, CSF=377 mL) was prepared using a reactor (FIG. 8) as shown in WO2018/047749. The liquid was reacted at a reaction initiation temperature of about 15° C. and an amount of carbon dioxide blown at 3 L/min, and the reaction was stopped when the pH of the reaction liquid reached 7-8. Carbon dioxide gas is supplied to an ultra-fine bubble generator (Fig. 9, shear type, Envirovision YJ-9), and a large amount of ultra-fine bubbles containing carbon dioxide gas (average particle size: 137 nm, existence time of bubbles: 60 minutes) above) were generated in the reaction liquid, and calcium carbonate particles were synthesized on the cellulose fibers by the carbon dioxide gas method to synthesize composite fibers of sample 6 (FIG. 10).

<Evaluation of composite fiber sample>
The obtained samples were evaluated by the following procedures.

The conjugate fiber slurry (3 g in terms of solid content) was suction-filtered using filter paper, and the residue was dried in an oven (105° C., 2 hours), and the fiber:inorganic particle weight ratio of the conjugate fiber was measured.

Further, after each composite fiber sample was washed with ethanol, it was observed with an electron microscope (Figs. 3 to 7, 10). As a result, it was observed that the inorganic substance covered the fiber surface and self-fixed in all the samples. The primary particle diameters of the inorganic particles estimated as a result of observation with an electron microscope are shown in Table 1 below.

Experiment 2. Manufacture of composite fiber sheet and chemical treatment <Manufacturing of composite fiber sheet>
The conjugate fibers of Samples 1 to 6 were sheeted by the following procedure. The basis weight of each sheet was measured according to JIS P 8124:1998, and the ash content was measured according to JIS P 8251:2003.

(Sheet 1) Sheet of sample 1 An anionic retention agent (FA230, Hymo) and a cationic retention agent (ND300, Hymo) are added to a composite fiber slurry (Sample 1, concentration: about 1%). A slurry (aqueous suspension) was prepared by adding 100 ppm per minute. Next, using a fourdrinier paper machine, a sheet was produced from this slurry at a machine speed of 10 m/min (basis weight: about 160 g/m ² , ash content: about 64%).

(Sheet 2) Sheet of Sample 2 A sheet of Sample 2 was produced using a Fourdrinier paper machine in the same manner as Sheet 1 (basis weight: about 100 g/m ² , ash content: about 43%).

(Sheet 3) Sheet of Sample 3 A sheet of Sample 3 was produced using a Fourdrinier paper machine in the same manner as Sheet 1 (basis weight: about 100 g/m ² , ash content: about 33%).

(Sheet 4) Sheet of Sample 4 In the aqueous suspension (about 0.5%) of Sample 4, 200 ppm of a cationic retention agent (ND300, manufactured by Hymo) and an anionic retention agent (FA230, manufactured by Hymo) ) was added at 200 ppm and stirred at 500 rpm to prepare a suspension. A composite fiber sheet was produced from the resulting suspension using a rectangular papermaking machine according to JIS P 8222 (basis weight: about 170 g/m ² , ash content: 61%).

(Sheet 5) Sheet of Sample 5 An aqueous suspension (approximately 0.5%) of Sample 5 was poured into a Buchner funnel set with filter paper (standard filter paper No. 5B, diameter 90 mm, manufactured by ADVANTEC). After standing still for 10 seconds, the wet paper obtained by suction filtration was dried to produce a composite fiber sheet (diameter: about 95 mm, basis weight: about 135 g/m ² , ash content: 18%).

(Sheet 6) Sheet of Sample 6 A sheet of Sample 6 was produced in the same manner as Sheet 5 above except that the aqueous suspension of Sample 6 was used (diameter: about 95 mm, basis weight: about 135 g/m ² , ash content : 56%).

<Flame-retardant treatment of sheet>
(a) Treatment of Sheet with Boron-Based Agent After spraying a boron-based agent (trade name: Soufa, manufactured by Soufa) on the following sheet sample, the excess agent was removed with a roller while sandwiched between a metal plate and aluminum foil. Then, it was transferred to a dryer and dried under tension at 60° C. for 1 hour to obtain a chemical-treated sheet.
・Composite fiber sheets (sheets 1 to 4)
・ Filter paper (manufactured by ADVANTEC, standard filter paper No. 1, 260 mm × 260 mm)
・ Copy paper (manufactured by FUJI XEROX, product name: EP GAAA5989, A4 size)
・Inkjet paper (manufactured by Nippon Paper Industries, matte IJ paper, A4 size)
(b) Treatment of sheet with silicon-based chemical Chemical treatment was performed in the same manner as in (a) above, except that the chemical to be treated was a silicon-based chemical (trade name: Crystal Sealer, manufactured by Bokuto Kasei Kogyo Co., Ltd.).
(c) Sheet treatment with phosphorus- and nitrogen-based chemicals After impregnating the following sheet samples with phosphorus- and nitrogen-based chemicals (trade name: Taien N, manufactured by Taiyo Kagaku Sangyo, 40 wt% aqueous solution), a metal plate and aluminum foil The excess drug was removed by pinching and rollers. After that, it was transferred to a dryer and dried under tension at 50° C. for 2 hours to obtain a chemical-treated sheet.
・Composite fiber sheet (sheet 5)
・ Filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm)
(d) Treatment of sheet with boron-containing chemical The following sheet samples were treated in the same manner as in (c) above, except that the chemical to be treated was a boron-containing chemical (trade name: UBCERA, manufactured by Ishizuka Glass Co., Ltd., 10 wt%). were treated with drugs.
・Composite fiber sheets (sheets 5 and 6)
・ Filter paper (manufactured by ADVANTEC, standard filter paper No. 5B, diameter 90 mm)

<Calculation of drug content>
The drug content rate (relative to the solid content) of the above drug-treated sheet was calculated according to the following formula.
Drug content (relative to solid content) [%] = (M ₁ - M ₀ )/M ₀
Here, M ₀ represents the absolute dry weight [g] of the sheet before chemical treatment, and M ₁ represents the absolute dry weight [g] of the sheet after chemical treatment.

<Flexibility evaluation of chemical-treated sheet>
The flexibility of the sheet before and after chemical treatment was evaluated. Specifically, with respect to the resistance felt when bending with both hands, the change in the flexibility of the sheet due to the chemical treatment was evaluated on a 4-point scale using the sheet before the chemical treatment as a reference. The evaluation criteria are as follows. A score of 4 indicates that the flexibility of the sheet was not impaired before and after the chemical treatment, and a score of 1 indicates that the sheet became hard and brittle due to the chemical treatment.
(Evaluation of suppleness)
・4 points: No change in flexibility before and after chemical treatment ・3 points: The sheet became slightly hard after chemical treatment ・2 points: The sheet became slightly hard after chemical treatment ・1 point: Chemical treatment rear seats hard

The results of evaluating the flexibility of each sheet are shown in the table below. Commercially available papers (inkjet paper, filter paper) treated with chemicals all tended to be extremely hard and extremely brittle sheets. On the other hand, samples 1 to 6 (composite fiber sheets) treated with chemicals were all flexible sheets compared to commercially available paper, and the effect of chemical treatment on flexibility was small. From this, it can be said that by using the composite fiber sheet as a base material, the flexibility of the fibers and the sheet is maintained even by chemical treatment.

Experiment 3. Combustibility Evaluation The combustibility of Sheets 1 to 4 obtained in Experiment 2 was evaluated by the following procedure based on JIS A 1322 (JIS Z 2150). First, each sample was dried at 50° C. for 48 hours, then left in a desiccator containing silica gel for drying for 24 hours, and subjected to the following combustibility test.
The sample was attached to a support frame (25 cm x 16 cm) and attached to the flammability test apparatus without slack. After igniting the gas burner, the sample was heated for 10 seconds or 1 minute, and the carbonization length, afterflame time, and afterflame time were measured (Fig. 11).

For the combustion test, a 45° flammability tester (FL-45M manufactured by Suga Test Instruments Co., Ltd.) was used. A Meckel burner (height: 160 mm, inner diameter: 20 mm) was used for heating, and only gas was supplied without mixing primary air for combustion. Liquefied petroleum gas No. 5 (based on butane and butylene, JIS K 2240) was used as the fuel, and the flame length was adjusted to 65 mm without attaching the sample.

Next, the heated specimens were evaluated according to JIS A 1322 (JIS Z 2150).
Charred length: Measure the maximum length of the supporting frame in the longitudinal direction of the charred portion of the heating surface of the specimen (the strength is clearly changed by charring).
・Afterflame time: Measure the time that the test piece continues to burn after the end of heating.
・Residue: A state of flameless combustion from the end of heating.
・Flameproof grade for flame retardancy ・Flameproof grade 1: char length 5 cm or less, no afterflame, no residue after 1 minute ・Flameproof grade 2: charlength 10cm or less, no afterflame, 1 residue Flameproof grade 3: char length 15 cm or less, no afterflame, no dust after 1 minute

The evaluation results are shown in the table below. While the non-chemically treated sheet did not meet the JIS standard (flameproof grade 3), all the chemically treated samples had a carbonization length of 5 to 10 cm. , the performance was equivalent to JIS flame retardant grade 2. From the above, it was suggested that a certain degree of flame resistance could be imparted to the composite fiber sheet by chemical treatment.

The combustibility of sheets 5 and 6 obtained in Experiment 2 was evaluated by the following procedure. First, each sample was dried at 70° C. for 3 hours, then left in a desiccator containing silica gel for drying for 2 hours, and subjected to the following combustibility test.
The upper part of the sample was attached to a clip, and the sample was allowed to stand in a suspended state. Then, a ignited lighter (flame length: 30 mm, not in contact with the sample) was quickly brought close to the bottom of the sample, and the sample was fixed in a state where the flame was in contact with the sample by 10 mm, and heating was continued for 5 seconds. (Fig. 12). Observe how the fire spread.

The evaluation results are shown in the table below. The non-chemical treated sheet burned with a violent flame, and almost no specimen remained in any of the samples, while the chemical-treated filter paper slightly ignited flames when heated. However, it self-extinguished in about 3 seconds with flameless combustion. On the other hand, in the chemically treated composite fiber sheet, no flaming or flameless combustion was observed in the sample, only the heated portion was carbonized, and the carbonized portion was small. From the above, it was suggested that the composite fiber sheet could be imparted with a certain level of flame resistance by chemical treatment in this experiment as well.

Experiment 4. Evaluation of inkjet (IJ) printability A pattern was printed using an IJ printer (Canon PIXUS iP7100, dye ink), and the IJ printability of the sample before and after chemical treatment was evaluated.

Specifically, the IJ printability of each sample was visually evaluated on a 5-point scale of 1 to 5 with respect to bleeding and color development of the IJ-printed pattern. The larger the numerical value, the better the printability, and the printability of commercial IJ paper not treated with chemicals was rated as "5".
(Bleeding) Good 5 (untreated IJ paper) → 1 Poor (color development) Good 5 (untreated IJ paper) → 1 Poor

The evaluation results are shown in the table. When normal paper (copy paper, IJ paper, filter paper) was treated with a flame retardant, the printability was significantly reduced, while the composite fiber sheets (sheets 1, 2, 4, 5) treated with a flame retardant could be printed in the same manner as before the chemical treatment. In particular, in Sheets 4 and 5, bleeding and coloring of the sheets after chemical treatment were good.

From the above, it was shown that by using a composite fiber sheet as a base material, deterioration of bleeding due to chemical treatment can be suppressed, and excellent print quality can be provided.

Experiment 5. Production and evaluation of composite fiber board <Production of molding using composite fiber>
Molded articles for use in exothermic tests were produced according to the following procedure. Treatment liquid A (boron-based chemical, trade name: BestBoron, manufactured by Soufa, 36 wt % aqueous solution) was used for the following board samples.

(Board 1)
An aqueous suspension of sample 1 was poured into a mold (144 mm×144 mm×100 mm) with a mesh bottom and compression molded to produce a board. This was pressed at 1 MPa for 1 minute, then at 3 MPa for 2 minutes, and then dried for 10 hours using a constant temperature bath set at 75°C. The resulting dry sample was cut into 100 mm squares, immersed in the treatment liquid A at 75° C. for 60 minutes, and then dried for 5 hours using a constant temperature bath set at 105° C. to produce a board 1. .

(Board 2)
A square prism mold (144 mm × 144 mm × 10 cm) with a mesh bottom was attached to the tip of the water-absorbing vacuum cleaner, and the mold was placed in a mixed aqueous suspension of sample 6 aqueous suspension and calcium carbonate (special grade, manufactured by Kanto Kagaku). Immediately after immersion in a resin container (25 L volume) containing a turbid liquid, suction was started. When the suction was applied for about 10 seconds, the mold was pulled up, and the suction was continued for 30 seconds. After the suction was completed, the contents were removed from the mold, pressed (1 MPa for 1 minute, then 3 MPa for 2 minutes), and then dried for 10 hours using a constant temperature bath set at 75°C. The resulting dry sample was cut into 100 mm squares, immersed in the treatment solution A at 75° C. for 60 minutes, and then dried for 5 hours using a constant temperature bath set at 105° C. to produce a board 2. .

(Board 3)
Board 3 was prepared in the same manner as for Board 2 above, except that an aqueous suspension of Sample 6 and a mixed aqueous suspension of Roseki Mitsuishi (manufactured by Takenobo Seiko) were used.

<Evaluation of composite fiber board>
According to ISO5660-1:2002, the total calorific value for 20 minutes in the cone calorimeter method and the dimensional shrinkage after the test were evaluated. In addition, if the following three points are satisfied, it can be judged that it corresponds to "noncombustible material" in the Building Standards Law. In addition, when "the amount of shrinkage of the sample after heating is greater than 5 mm", it was evaluated as having "harmful deformation".
(Evaluation item)
・Total calorific value of 8 MJ/m ² or less ・No harmful deformation, cracks or holes penetrating to the back (evaluated based on appearance and shrinkage of sample after heating)
・The maximum heat generation rate must not exceed 200 kW/m ² continuously for 10 seconds or more.

The results of evaluation according to the above evaluation items are shown in the table, and all of the chemical-treated boards 1 to 3 satisfied all the evaluation criteria. Therefore, it was suggested that it has fire resistance equivalent to noncombustible materials.

From the above, it was shown that by producing a board using a composite fiber sheet as a base material using a noncombustible treatment liquid, it is possible to develop fire resistance equivalent to that of noncombustible materials in the Building Standards Act.

Also, if a pattern was applied to the mold during molding, a board with an uneven pattern could be obtained.

Claims (10)

15% or more of the cellulose fiber surface is coated with inorganic particles , a composite fiber containing a flame retardant,
The average primary particle diameter of the inorganic particles is 1.5 μm or less, the inorganic particles are at least one selected from the group consisting of hydrotalcite, calcium carbonate, silica/alumina, and aluminum hydroxide, and the flame retardant is , a boron-based flame retardant, a silicon-based flame retardant, a phosphorus-based flame retardant, and a nitrogen-based flame retardant . The composite fiber according to claim 1, wherein the flame retardant is a boron-based flame retardant or a silicon-based flame retardant. The composite fiber according to claim 1 or 2 , wherein the flame retardant is a phosphorus-based flame retardant and/or a nitrogen-based flame retardant . The composite fiber according to any one of claims 1 to 3 , wherein the inorganic particles contain hydrotalcite . A composite fiber according to any one of claims 1 to 4 , wherein the inorganic particles comprise calcium carbonate or silica/alumina. The composite fiber according to any one of claims 1 to 5 , wherein the weight ratio of cellulose fibers to inorganic particles is from 5/95 to 95/5. A sheet, mold, board or block comprising the composite fiber according to any one of claims 1-6 . A method for producing a composite fiber according to any one of claims 1 to 6 ,
The above method, comprising the step of treating the composite fibers of inorganic particles and cellulose fibers with a flame retardant. 9. The method of claim 8 , wherein the flame retardant is included in the composite fiber by impregnation , coating or spraying. 10. A method according to claim 8 or 9 , comprising synthesizing inorganic particles in a liquid containing cellulose fibers to obtain said composite fibers.

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